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Old Oct 23, 2010, 04:01 AM
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Cornwall UK
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Quad frame idea for safety

Hi Guys,
I am just about to build my first quad for aerial photography (maybe the x650 when some of you have reviewed it first!). I have 35 years rc experience with planes and hellis. Has anyone used aerofoils for the booms on their quad? My theory is the quad would "helicopter" down like a sycamore seed. I know the wind would affect it a little but if I am 400 ft up and everything fails, at least is will fall a bit slower! I see lots of talk about parachutes but this seems simpler. What do you guys think?
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Old Oct 23, 2010, 04:40 AM
WHEN IN DOUBT FLOOR IT!!!
G-unit's Avatar
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wouldn't the air from the props make it want to spin in flight..
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Old Oct 23, 2010, 05:00 AM
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If you want to be safer, build a well thought out Octo using a good FCB. Not some cheap, unproven quad design.
Here is a link of my Octo with a UAVX FCB losing a motor in flight.
Fun Flying (1 min 54 sec)

This video was made in 15 plus mph winds, the Octo was very controllable once I realized what happened. I will be ready even quicker if it happens again.
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Old Oct 23, 2010, 05:06 AM
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Originally Posted by andrewonline View Post
Hi Guys,
I am just about to build my first quad for aerial photography (maybe the x650 when some of you have reviewed it first!). I have 35 years rc experience with planes and hellis. Has anyone used aerofoils for the booms on their quad? My theory is the quad would "helicopter" down like a sycamore seed. I know the wind would affect it a little but if I am 400 ft up and everything fails, at least is will fall a bit slower! I see lots of talk about parachutes but this seems simpler. What do you guys think?
Interesting idea. If it did work it would probably require the quad to be perfectly level when all the power goes out which usually doesn't happen. The arms of a quad are also relatively short compared to a helicopter so I doubt they would be effective in helping the quad autorotate. It would be nice to see it tried though.
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Last edited by RCvertt; Oct 23, 2010 at 05:58 AM.
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Old Oct 23, 2010, 05:39 AM
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Cornwall UK
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that's got you all thinking!!! I might find time this week to make up a test frame with similar weights and throw it off the nearby cliff. With a bit of tape,sticks, glue and depron sheet I could get a few tries before binning it. If it doesn't work, no great loss. And if the wind is blowing I can do some slope soaring while i am there.
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Old Oct 23, 2010, 05:46 AM
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that's got you all thinking!!!
LOL, No, not really.
Anything added to the copter that could allow it to glide down in any way would also grab the wind and prop wash in flight. This would make it useless as an AV platform. But I am sure you will make some funny videos of your + shaped freesbie for us.
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Old Oct 23, 2010, 06:43 AM
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all good fun. I will video it but it might make me famous for all the wrong reasons if it fails badly lol
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Old Oct 23, 2010, 07:21 AM
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all good fun. I will video it but it might make me famous for all the wrong reasons if it fails badly lol
Don't worry bro, you will be in good company, I am proud of a controlled crash video.
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Old Oct 23, 2010, 07:33 AM
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In the full scale aviation industry redundancy is the best safety measure. Simply put, the system may fail but only partially, leaving enough to keep control for a safe, if somewhat less than perfect return to earth.
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Old Mar 06, 2011, 11:14 AM
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if you had an independently powered accelorometer that caused a servo to kick in once you hit max rate of fall caused by gravity and your servo connected to a parachute release or "unfurled" your airfoils, I could see this working.

Youd have to be damn cool to make that happen tho
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Old Mar 06, 2011, 03:43 PM
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I think you're attempting to solve a problem without understanding what the problem actually looks like.

What's the most common mode of failure for a quad? All power lost? Or just one or two motors lost?

Isn't the weight distribution of a quad going to be a problem? A lot of mass is on the ends of the booms. Compare to a helicopter or autogyro where the mass isn't even in the rotor itself, or a sycamore seed where the mass is more central to the rotation.

You're going to probably need to extend your airfoils out past your current booms.
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